package com.tssup.fesco.common.frame.mybatis.dialect;

/**
 * Mybatis Oracle分页
 */
public class OracleDialect extends Dialect {

    @Override
    public boolean supportsLimit() {
        return true;
    }

    @Override
    public boolean supportsLimitOffset() {
        return true;
    }

    @Override
    public String getLimitString(String sql, int offset, String offsetPlaceholder, int limit, String limitPlaceholder) {
        sql = sql.trim();
        boolean isForUpdate = false;
        if (sql.toLowerCase().endsWith(" for update")) {
            sql = sql.substring(0, sql.length() - 11);
            isForUpdate = true;
        }

        StringBuffer pagingSelect = new StringBuffer(sql.length() + 100);
        if (offset > 0) {
            pagingSelect.append("select * from ( select row_.*, rownum rownum_ from ( ");
        } else {
            pagingSelect.append("select * from ( ");
        }
        pagingSelect.append(sql);
        if (offset > 0) {
            String endString = offsetPlaceholder + "+" + limitPlaceholder;
            pagingSelect.append(" ) row_ ) where rownum_ <= " + endString + " and rownum_ > " + offsetPlaceholder);
        } else {
            pagingSelect.append(" ) where rownum <= " + limitPlaceholder);
        }

        if (isForUpdate) {
            pagingSelect.append(" for update");
        }

        return pagingSelect.toString();
    }

}
